Control system



H. G. MOORE CONTROL SYSTEM Feb. '4, 1941.

Filed July 25, 1940 is Attorney.

Patented Feb. 4, 1941 UNITED STATES PATENT OFFICE CONTROL SYSTEM Harold G. Moore, Wesleyville, Pa., assignor to General Electric Company, a corporation of New York Application July 25, 1940, Serial No. 347,459

6 Claims. (Cl. 172179) My invention relates to control systems for Also the field windings are connected in series electric vehicles such as electric buses, railway with each other through the supply source and cars and the like, particularly to dynamic brakin series with a resistor 25, one field of each pair ing motor control systems for direct current being reversed so that the generator voltages of series motors, and has for its object a simple and each pair of motors are in the same direction. 5 reliable control system for a plurality of parallel Consequently currents are generated by each pair connected motors. of motors through the respective braking resistor I have shown my invention in one form as apfor dynamic braking. plied to two pairs of parallel connected motors In the operation of the system, the motors are 10 with each pair of which I provide a braking restarted by moving the controller 25a from its oil 1 sistor permanently connected across the pair of position to its. first position closing a switch 25 motors. Because the motors of each pair have to energize the P switch coil 2! and the LB switch the same polarity during acceleration, no current coil 28 in series with each other. This control flows through the braking resistor during accelcircuit leads from the supply main it through eration. For dynamic braking operation I enerthe switch 26, the B switch 29, the P coil 2'3, the 15 gize the fields of the motors in series with each LB coil 28, the OLR switch 30, which is normally other from the supply source with one field of closed, a switch 3| which is closed to the supply each pair reversed whereby the sum of the voltmain is. The switch 3! is in the manually opages of each pair of motors operating as genererated controller 25a and is closed by a cam 31a ators is .applied to its braking resistor. Also I when the controller is in any operative position, 20 provide for automatic adjustment of the dynamic although when the controller is moved to an on" braking by connecting one of the motors in the position the switch 3! is open as shown. If the field circuit with its voltage in opposition to the switch 26 is already closed, the coils 2'! and 28 voltage of the supply source. are energized when the controller a, is turned 25 For a more complete understanding of my infrom its oil? position to its first position. to close 25 vention, reference should be had to the accomthe switch 3|. panying drawing in which Fig. 1 is a diagram- When energized, the coil 28 closes the LB matic representation of a vehicle drive control switch 33 in'the circuit of the motors and an system embodying my invention while Fig. 2 is a interlock switch 34 around the switch 3!, while simplified diagram of connections of the dynamic the P .coil 27 closes the switches 35, 35 and 3'. in 30 braking circuits. the individual motor circuits and a switch 39 in Referring to the drawing, I have shown my the circuit of one pair l2, [3 of the motors. This invention in one form as applied to twopairs connects the motors in parallel with each other, of series direct current motors having armatures the Ci cuit leading f om the a s through t e 35 i0, H and l2, l3, and being provided with series LB switch 33, the OLR coil it, through the con- 85 fields l4, l5 and I6, IT. For motoring operation, troller 25a, the two starting resistors 4| and 42 these motors are connected in parallel with each in parallel with each other, and thence through other to direct current supply mains I8 and 19, the switch 39 to motor fields I6 and H and motor the supply main l8 being connected through a armatures l2 and I3 to the main It. A parallel 40 suitable trolley connection device 20 to a trolley circuit exists from starting resistor and i2 and 40 conductor 2i, while the supply main I9 is con- .thence through the motor fields l4 and i5 and nected to a ground connection 22. Also during motor armatures l0 and II to the main is. The motoring operation, each field winding is conacceleration of the motor is effected by turning nected in circuit with its associated armature. the controller by means of a handle 63 so as to Two dynamic braking resistors 23 and 24 are successively short out or exclude sections of the 45 connected permanently and respectively across resistors 4| and 42 by suitable switches (not equal voltage points on the high voltage unshown) and thereby accelerate the motors. grounded sides of the pairs of armatures II], II For dynamic braking, the switch 28 is opened and I2, l3. During motoring operation, since the to deenergize the coils 21 and 28 and thereby to voltages of the motors are equal, no potential open the motoring switches. Then a switch 44 difference appears across the braking resistors is closed to energize the pp Section 45 O t e and therefore no current flows through them. B switch coil, this circuit from the main I8 For dynamic braking operation, the armatures through the switch 44, the LOR switch 46, the of the motors (except one) are disconnected from coil section 45, the LB switch 4'! and thence to their field windings and from the supply source. the main I 9. Thereupon the coil closes the 6C B switches 48' and 49 to establish the dynamic braking connections for the motors.

At the same time the coil 45 closes its interlock switch 50 which, in turn, energizes the LOR coil 5|. The LOB coil 5| thereupon opens its switch 46 to deenergize the coil section 45 and closes its switch 52 thereby connecting the B coil section 53 across the motor I!) whereby the switches 48 and 49 are maintained closed by the voltage across the motor I0 acting as a generator. This circuit for the coil section 53 leads from the high potential side of the motor armature l0 through the conductor 54, the switch 52, the coil 53, the conductor 55, the switch 41 and thence to the supply main l9 on the other side of the motor I9. Therefore the coil 53 is energized sufficiently to maintain the braking switches 48 and 49 closed and maintain dynamic braking as long as the voltage of the motor I0 and hence the speed of the vehicle, are above predetermined limits. The vehicle speed limit may, for example, be 5 or 10 miles per hour.

The dynamic braking connections are now as shown in Fig. 2. They may be traced in Fig. 1 from the main I8 through the conductor 56, the switch 48, the field resistor 25, the field winding I4, which is thus reversed, the field winding 15, the switch 49, the field winding I6 which is reversed, the field winding I! and the motor armature [3 to the main l9 and thence to ground. Furthermore, the motor armatures l0 and II are connected in series relation with each other across their dynamic braking resistor 23 while motor armatures l2 and I3 are connected in series relation with each other across their dynamic braking resistor 24.

The voltage of the armature I3 opposes the voltage of the supply mains I8 and I9. Consequently as the speed and the voltage oi the armature l3 decreases, the current through the field windings increases to maintain thereby a substantially constant dynamic braking effort over a wide range of vehicle and motor speeds. The conductor 55 may be connected to any suitable low-voltage supply source, such as a battery or a generator with corresponding reduction in ohmic value of resistor 25. This reduces the energy loss in this resistor.

In the event of an overload current in the motor circuit greater than a predetermined maximum value, the OLR coil 49 picks up its armature, opening the switch 30 to deenergize the motors and closing the switch 51. The switch 5! establishes a circuit through the OLR coil 58 which holds the switch 39 open and the switch 5'! closed until such time as switch 26 is opened for restarting of the motors.

An LOB switch 59 which is normally open is also provided. This switch is closed when the coil 5| is energized, and thereby closes a holding circuit around the switch 59 for the coil 5|. Therefore the coil 5| is maintained energized when the switch 50 subsequently opens and until the control switch 44 is Opened.

The control switch 44 is manually operated and may be connected to a pedal. Also the switch 25 may be manually operated. Preferably the switch 26 is actuated with the controller 25a in a well-known manner such that the switch 26 is closed whenever the handle 43 is turned from the ofi-position toward the full running position. Any reverse movement of the handle, however, opens the switch 25. This operates to deenergize the coils 21 and 28 and thus open the motor circuit so that there will be no arcing in the controller 25a when it is turned in the reverse direction to reinsert the resistors 4| and 42 in the circuit.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto, since many modifications may be made and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric motor control system comprising a pair of driving motors each provided with an armature and a field winding, connections for connecting said motors in circuits in parallel with each other to a source of electric supply for motoring operation, a dynamic braking resistor connected to equal voltage points of said motors, and means for disconnecting said armatures from the source of supply and for reversing the polarity of one of said armatures for dynamic braking operation.

2. An electric motor control system comprising a pair of driving motors each provided with an armature and a series field winding, connections for connecting said motors in circuits in parallel wtih each other to a source of electric supply with the field winding of each motor in series with its armature for motoring operation, a dynamic braking resistor connected to said motors across equal voltage points of said circuits, and switching means for disconnecting said armatures from the source of supply and for reversing the polarity of one of said armatures for dynamic braking operation.

3. An electric motor control system comprising a pair of driving motors each provided with an armature and a field winding, connections for connecting said motors in circuits in parallel with each other to electric supply conductors for motoring operation, a dynamic braking resistor permanently connected to said motors across equal voltage points of said circuits, means for disconnecting like terminals of said armatures from one of said supply conductors and for reversing one of said field windings for reversed polarity of one of said armatures for dynamic braking.

4. An electric motor control system comprising a pair of driving motors each provided with an armature and a field winding, connections for connecting said motors in circuits in parallel with each other to electric supply conductors for motoring operation, a dynamic braking resistor permanently connected to said motors across equal voltage points of said circuits, means for disconnecting like terminals of said armatures from one of said supply conductors and for reversing one of said field windings for reversed polarity of one of said armatures and with the other of said armatures in circuit with at least one of said field windings so that said armatures supply dynamic braking current through said braking resistor and said dynamic braking current is regulated in accordance with the voltage of said other armature.

5. An electric vehicle control system comprising a pair of driving motors each provided with an armature and a series field winding, connections for connecting said motors in circuits in parallel with each other to a source of electric supply with the field winding of each motor in series with its armature for motoring operation, a dynamic braking resistor permanently connected to said motors across equal voltage points of said parallel circuits, switching means for disconnecting one terminal of one of said armatures from the source of supply and from its field winding, and connections for connecting said field windings in series with each other with the connections of one of said field windings reversed with respect to said other field winding to an electric source of energy supply in series with the other of said armatures whereby said motors supply dynamic braking current through said braking resistor and the dynamic braking current is regulated in accordance with the voltage of said other armature.

6. An electric vehicle control system comprising at least two pairs of driving motors each motor being provided with an armature and a series field Winding, connections for connecting said motors in circuits in parallel with each other to a source of electric supply with the field winding of each motor in series with that motor, a. dynamic braking resistor permanently connected to each of said pairs of motors across equal voltage points of said circuits, means for disconnecting said armatures from the source of supply and for reversing one of the field windings of each pair for reversed polarity of one armature of each pair and with the other armature of one pair in circuit with said field windings so that said armatures supply dynamic braking current through said braking resistors and said dynamic braking current is regulated in accordance with the voltage of said other armature.

HAROLD G. MOORE. 

